Initial exploration around jit

Author: ClementWalter

cairo/jit/main.cairo

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+from starkware.cairo.common.alloc import alloc
+from starkware.cairo.common.registers import get_label_location
+from starkware.cairo.lang.compiler.lib.registers import get_fp_and_pc
+
+// Compiled Instructions
+const CALL_ABS = 0x1084800180018000;
+
+// Modified return instruction to update the offset of return_pc.
+// Putting an offset >= 0 let's dynamically chose where to return.
+// Offset = -1 is the default ret opcode.
+const RET_FP_OFFSET_HIGH = 0x208b8000;
+const RET_FP_OFFSET_LOW = 0x7fff7ffe;
+const RET = (RET_FP_OFFSET_HIGH - 1) * 256 ** 4 + RET_FP_OFFSET_LOW;
+const RET_0 = (RET_FP_OFFSET_HIGH) * 256 ** 4 + RET_FP_OFFSET_LOW;
+
+// Bytecode Opcode
+const OP_JUMP4 = 0;
+const OP_RET = 1;
+const OP_PUSH = 2;
+const OP_PC = 3;
+const OP_CALL = 4;
+const OP_ADD = 5;
+const OP_MUL = 6;
+
+func compile(input: felt, code_len: felt, code_ptr: felt*) -> (
+    compiled_code_len: felt, compiled_code_ptr: felt*
+) {
+    alloc_locals;
+    let (local op: felt*) = get_label_location(opcodes_location);
+    let (local compiled_code) = alloc();
+    if (code_len == 0) {
+        return (0, compiled_code);
+    }
+
+    tempvar i = 0;
+    tempvar compiled_code = compiled_code;
+
+    loop:
+    let i = [ap - 2];
+    let compiled_code = cast([ap - 1], felt*);
+
+    let code_len = [fp - 4];
+    let code = cast([fp - 3], felt*);
+    let op = cast([fp], felt*);
+
+    tempvar opcode_number = code[i];
+    assert [compiled_code] = CALL_ABS;
+    assert [compiled_code + 1] = cast(op + 2 * opcode_number + op[2 * opcode_number + 1], felt);
+
+    tempvar is_push = opcode_number - OP_PUSH;
+    jmp not_push if is_push != 0;
+
+    push:
+    assert [compiled_code + 3] = code[i + 1];
+    tempvar stop = code_len - i - 2;
+    tempvar i = i + 2;
+    tempvar compiled_code = compiled_code + 4;
+    jmp loop if stop != 0;
+    jmp end;
+
+    not_push:
+    tempvar stop = code_len - i - 1;
+    tempvar i = i + 1;
+    tempvar compiled_code = compiled_code + 2;
+
+    static_assert i == [ap - 2];
+    static_assert compiled_code == [ap - 1];
+    jmp loop if stop != 0;
+    jmp end;
+
+    end:
+    let i = [ap - 2];
+    let compiled_code = cast([ap - 1], felt*);
+    assert [compiled_code] = RET;
+
+    let compiled_code = cast([fp + 1], felt*);
+
+    return (i, compiled_code);
+}
+
+func main() {
+    alloc_locals;
+
+    let (bytecode_start) = alloc();
+    let bytecode = bytecode_start;
+    assert [bytecode] = OP_JUMP4;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_PUSH;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_PC;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_PC;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_CALL;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_ADD;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_MUL;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+
+    tempvar input = 0xdead;
+    let (compiled_code_len, compiled_code_ptr) = compile(
+        input, bytecode - bytecode_start, bytecode_start
+    );
+
+    call abs compiled_code_ptr;
+    let result = [ap - 1];
+    assert result = 2;
+
+    return ();
+}
+
+func op_jump(input: felt) -> felt {
+    alloc_locals;
+    local return_pc;
+    tempvar jump_size = 4;
+    assert return_pc = [fp - 1] + 2 * jump_size;
+
+    tempvar result = 0;
+
+    dw RET_0;
+}
+
+func op_ret(input: felt) -> felt {
+    alloc_locals;
+    local main_return_pc;
+
+    let return_fp = [fp - 2];
+    main_return_pc = [return_fp - 1];
+
+    tempvar result = input;
+    dw RET_0;
+}
+
+func op_push(input: felt) -> felt {
+    alloc_locals;
+    // [fp - 1] is next CALL_ABS instruction
+    // [[fp - 1] + 1] is the word to push
+    // [fp - 1] + 2 where to move the PC after the push
+    local return_pc = [fp - 1] + 2;
+    tempvar word = [[fp - 1] + 1];
+
+    dw RET_0;
+}
+
+func op_pc(input: felt) -> felt {
+    let return_pc = [fp - 1];
+    let calling_pc = return_pc - 2;
+    let return_fp = [fp - 2];
+    let main_return_fp = [return_fp - 2];
+    let compiled_code_ptr = [return_fp - 3];
+
+    return (calling_pc - compiled_code_ptr) / 2;
+}
+
+func op_call(input: felt) -> felt {
+    let (bytecode_start) = alloc();
+    let bytecode = bytecode_start;
+    assert [bytecode] = OP_PC;
+    let bytecode = bytecode + 1;
+    assert [bytecode] = OP_RET;
+
+    let (compiled_code_len, compiled_code_ptr) = compile(
+        input, bytecode - bytecode_start, bytecode_start
+    );
+
+    call abs compiled_code_ptr;
+    ret;
+}
+
+func op_add(input: felt) -> felt {
+    let result = input + 1;
+    return result;
+}
+
+func op_mul(input: felt) -> felt {
+    let result = input * 2;
+    return result;
+}
+
+// Create a label and a list of call rel op to be able to get all the opcodes locations
+// with a single call to get_label_location.
+opcodes_location:
+call op_jump;
+call op_ret;
+call op_push;
+call op_pc;
+call op_call;
+call op_add;
+call op_mul;

cairo/tests/jit/test_main.py

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+class TestMain:
+
+    def test_main(self, cairo_run):
+        cairo_run("main")